Physical Unclonable Functions (PUFs) are increasingly used for authentication and identification applications as\ well as cryptographic key generation. An important feature\ of a PUF is the reliance on minute random variations in the\ fabricated hardware to derive a trusted random key. Currently,\ most PUF designs focus on exploiting process variations intrinsic\ to CMOS technology. In recent years, progress in emerging\ nanoelectronic devices has demonstrated an increase in variation\ as a consequence of scaling down to the nano region. To\ date, emerging PUFs with nanotechnology have not been fully\ established, but they are expected to emerge. Initial research\ in this area aims to provide security primitives for emerging\ integrated circuits with nanotechnology. In this paper, we review\ emerging nanotechnology-based PUFs